There has been widely used a technique in which a dielectric substance called a solder resist is applied to a portion which is not soldered in a board mounted with an SMT (Surface Mount Technology) component so that solder is restricted from extending over the board.
On the other hand, when the solder resist serving as a dielectric substance is disposed near a wiring section in a board mounted with a high frequency circuit element (high frequency circuit chip) and a board for a high frequency antenna module, dielectric loss of the solder resist leads to high-frequency transmission loss. An example of a wiring board covered with a solder resist layer is shown in FIG. 41(a) and FIG. 41(b).
In a wiring board 1 for a high frequency antenna module, a wiring section 3 and a back wiring section 7 are formed in front and back surfaces of a dielectric layer 4, and a surface mount type component such as a chip component 2 is mounted.
A solder resist layer 5 serving as a dielectric substance is disposed near the front-surface wiring section 3 mounted with the surface mount type chip component 2 so that solder 6 cannot spread over the board. However, dielectric loss of the solder resist layer 5 leads to high-frequency transmission loss. In addition, increase in effective dielectric constant caused by the solder resist layer 5 leads to reduction in effective wavelength so as to increase the transmission loss.
A technique described in Patent Literature 1 has been known as a mounting method relating to the module board. According to the mounting method in Patent Literature 1, manufacturing of a module has been disclosed as follows. That is, a solder resist layer is applied to a board during manufacturing of the board, and an SMT component is mounted on the board by soldering. After that, the solder resist layer is entirely removed by a solvent. Thus, loss in high frequency characteristics can be suppressed in the module.